I remembered that I could use ldd to find out what libraries hexchat is linking against. It's a long list, so I only downloaded debug symbols for likely-looking packages. Unfortunately, that didn't give me a better stack trace. When I get more time, I'll try additional debug packages.
I did figure out how to work around the crashes that I'm seeing. (I don't know if this helps for the crashes that the original submitter was seeing.) In $HOME/.config/hexchat/hexchat.conf, change gui_join_dialog = 1 to gui_join_dialog = 0 regards, mike